A Novel On-Chip Oil Swelling Measurement Platform for Gas Injection EOR Processes

Abstract

Abstract Oil swelling test data is essential to tune the EOS models to simulate gas injection EOR processes and evaluate the reservoir-scale recovery performances. PVT cells are typically used to measure this property; however, it may involve some challenges with runtime, fluid handling, and test operations. Here, a high-pressure high-temperature microfluidic approach is developed to measure the oil swelling in response to gas exposure under step-wise increasing pressure with different injection gas mole fractions. The microfluidic chip consists of a high-throughput gas-in-oil slug generator that produces multiple isolated gas-in-oil compound slugs with known initial volumes of gas and oil phases, each representing a single mixing condition that can be tested for oil swelling measurements. These isolated gas-in-oil compound slugs are generated at a pressure slightly higher than the oil bubble point pressure to ensure that oil remains in single-phase. A high-resolution microscopic camera is utilized to record time-lapse images of the volume at elevated pressures and the swelling factor is measured at the corresponding saturation pressure. Additionally, liquid volume fraction and relative volume are measured at each pressure step. The range of the data can be broadened so that the saturation pressure curve covers both bubble and dew points, representing both oil and retrograde gas condensate phase behaviors of single-phase fluid once reservoir oil and injection gas are fully mixed. The microfluidic swelling test results are also compared with those obtained with the conventional PVT cell, exhibiting a promising agreement between the measured data (i.e., average of ~5% deviation). While the PVT cell method may require several weeks to provide a full oil swelling dataset, the microfluidic approach developed here is notably faster and easier to operate for different types of reservoir oils and injection gases, stemming from small volume of fluid samples required for the testing procedure. The novel microfluidic platform developed here provides a unique opportunity to rapidly measure the large-scale oil swelling data, which has not been historically obtainable using conventional PVT cell. It can also facilitate tailoring and optimizing the injection gas through fast and accurate access to the relevant swelling data, informing the operators to better design gas injection projects. This can make gas injection PVT data accessible by an order of magnitude reduction in time, cost, and sample size requirements - in stark comparison with conventional methods.